If your opponent's hand is almost full and has a view minions on the board, when this card gets played, the cards that get bounced back and the ones that die are random. So sometimes a Deathrattle minion would die, other times it wouldn't. You understand where I'm getting at?

So why can't it be changed so the minions that get bounced back are prioritized from left to right?

They are not random, they are bounced in the order you have played them. Just like when you have Redemption active and your opponent plays an AOE spell, the minion that is resurrected is the first one you have played